Construction of Magneto‐Fluorescent Bifunctional Spin‐Crossover Fe(II) Complex from Pyrene‐Decorated Pybox Ligand

The construction of magneto‐fluorescent bifunctional complexes is a feasible approach toward multifunctional molecular materials. Herein we report the synthesis and properties studies of a mononuclear Fe(II) complex [FeL2](ClO4) (1), where L is a pyridine‐2,6‐bis(oxazoline) (pybox) ligand decorated by the pyrene fluorophore. Magnetic susceptibility measurement of desolvated complex 1‐d shows an incomplete and gradual spin‐crossover in the temperature range 50–300 K, which is further confirmed via 57Fe Mössbauer spectroscopy study. Light‐induced excited spin state trapping (LIESST) is also observed below 70 K when the powder sample is irradiated by a 532 nm laser. The change in absorption during the spin‐crossover (SCO) process is investigated via the temperature‐dependent UV‐vis spectroscopy. As expected, through introducing the chromophore, 1 displays fluorescence in both solution and solid state, achieving the coexistence of spin‐crossover and fluorescence in one compound. A magneto‐fluorescent bifunctional Fe(II) complex is synthesized through decoration of the pyrene fluorophore to Fe(II)‐pybox moiety. Its magnetic and fluorescent properties are characterized via X‐ray structural analyses, magnetic susceptibility measurement, 57Fe Mössbauer spectroscopy, and fluorescent spectroscopy. As expected, the coexistence of spin‐crossover and fluorescence is achieved.